A subject""s visual attention can be tested by displaying a series of visual stimuli, to which the subject is instructed to respond. Typically, the stimuli are of two types, and the subject is instructed to respond to only one of them. Data are collected for each stimulus presented including the type of stimulus, whether or not the subject responded, and if so, how long the subject took to respond. The continuous performance attention task has been in use since the mid 50""s (Rosvold et al., 1956, J. of Consulting and Clinical Psychology, 20: 343-350), with computerized versions available in the 1970""s (Greenberg, 1987, 23: 279-282). The previous methods of analysis of the raw data generated from these methods have typically distilled the data into a few numbers which do not capture the subject""s fluctuations in attention.
Another method for assessing the visual attention capabilities of a subject involves determining how long a particular visual stimulus must be present before a subject can detect it (U.S. Pat. No. 5,801,810). This method does not reveal the attentional state of the subject, rather, it requires the subject to be fully attentive.
Other reported methods determine a subject""s intensity of focused attention, concentration, and/or interest by measuring signals naturally emanating from the brain (U.S. Pat. Nos. 5,983,129 and 5,377,100). These brainwaves vary across subjects and even within the same subject; thus, these methods do not provide a reliable, well-defined number for classifying attentional states.
A diagnostic assessment of psychological conditions can be made by conducting a sequence of continuous performance tasks where information is recorded to reflect the number of target stimuli correctly identified, the number of target stimuli missed, the number of responses to non-target stimuli, the number of non-target stimuli correctly missed, and the final interstimulus interval (U.S. Pat. No. 5,940,801). This method can be used in a clinical setting, as well as remote locations such as the home, school, or workplace. Using this method in remote locations is useful for psychological and behavioral problems that are highly stimulus-dependent and may not be manifested in a clinical environment, such as depression, anxiety, schizophrenia, addiction, eating disorders, attention deficit disorders, attention deficit and hyperactivity disorder. This method does not provide a way to classify performance into states.
The aforementioned methods do not accurately quantify a subject""s attentional state. None classify a subject""s behavior into specific well-defined states or examine fluctuations in attention over time.
In one aspect, the invention features a method of acquiring information about the attentional state of a subject. The method involves (a) presenting to the subject a sequence of a predetermined number of stimuli over a predetermined period of time, wherein the sequence includes target and nontarget stimuli, (b) scoring the response of the subject on the percentage of targets responded to and the percentage of nontargets responded to, and (c) on the basis of the scoring of step (b), making a determination of the attentional state of the subject.
This method can be used to assess both overall attention and impulsivity. This method can be repeated three or more times to determine the pattern of attentional states and the time spent in each state.
This method can be used to diagnose the subject being tested for a psychological, neurological, or behavioral disorder, such as depression, an anxiety disorder, schizophrenia, a drug addiction, an eating disorder, an attention deficit disorder, an attention deficit and hyperactivity disorder, a learning disorder, or Alzheimer""s disease, dementia, epilepsy, stroke or traumatic brain injury. This method can be used to identify a subject at risk for a psychological, neurological, or behavioral disorder or to diagnose a subject with such a disorder. Additionally, this method can be used to determine the preferred therapy for the treatment of a psychological, neurological, or behavioral disorder or to correlate the attention state of a subject involved in a clinical trial of a therapy for a psychological or behavioral disorder with the success or failure of the therapy to improve the subject""s condition.
This method can also be used to assess the eligibility of a subject to obtain a driver""s license or a volunteer or paid position, including those that require a longer than average attention span, such as, an air traffic controller, pilot, emergency room doctor, surgeon, police officer, military officer, or fire-fighter.
In a related aspect, the invention features a method of determining whether a therapy affects the attentional state of a subject. This method involves (a) presenting to the subject undergoing treatment with the therapy a sequence of a predetermined number of stimuli over a predetermined period of time, wherein the sequence comprises target and nontarget stimuli, (b) scoring the response of the subject on the percentage of targets responded to and the percentage of nontargets responded to, and (c) on the basis of the scoring of step (b), making a determination of the attentional state of the subject. An altered attentional state, compared to either the attentional state of the subject when not undergoing treatment with the therapy or the attentional state of a control subject when not undergoing treatment with the therapy, indicates that the therapy affects the attentional state of the subject.
In one embodiment of this aspect, both overall attention and impulsivity are assessed. This method may be repeated three or more times to determine the pattern of attentional states and the time spent in each state. This method may also further include comparing the effect of the therapy on the attentional state of the subject to the effect of another therapy on the attentional state of the subject. Additionally, this method may further involve comparing the attentional state of a subject diagnosed with a disorder to that of a subject not diagnosed with the disorder.
In various embodiments, the subject is diagnosed with a psychological or behavioral disorder, such depression, an anxiety disorder, schizophrenia, drug addiction, an eating disorder, attention deficit disorder, attention deficit hyperactivity disorder, a learning disorder, Alzheimer""s disease, dementia, epilepsy, stroke, or traumatic brain injury. In other embodiments, the subject is involved in a clinical trial of a therapy for a psychological, neurological, or behavioral disorder. This method may be also used to determine the preferred therapy for the treatment of a psychological, neurological, or behavioral disorder.
In one desirable embodiment of any of the methods of the invention, the stimuli are visual symbols or audio sounds. The symbols can be individual numbers, letters, or shapes, or a combination of the above. Preferably, the stimuli are presented using a computer screen or speaker and the subject""s responses are recorded using a computer. In another desirable embodiment of the invention, the stimuli number 15, 20, 30, or greater within each analysis period. The test may be conducted in a clinical setting or across a network.